Non-invasive imaging techniques are widely used in security screening, quality control, and medical diagnostic systems. Particularly, in medical imaging, non-invasive imaging techniques such as multi-energy imaging allow for unobtrusive, convenient and fast imaging of underlying tissues and organs. To that end, radiographic imaging systems such as nuclear medicine (NM) gamma cameras, computed tomography (CT) systems and positron emission tomography (PET) systems employ a plurality of radiation sources and detectors.
CT systems, for example, typically include an X-ray source and a detector array that may be configured to acquire projection data from different angular positions around the object using a rotatable gantry or by rotating the object. Particularly, the detector array in a CT system employs one or more elements for converting X-ray photon energy into current signals that are integrated over a time period, measured, and ultimately digitized. Certain CT systems include photon counting (PC) detectors that provide dose efficient X-ray spectral information, energy discrimination (ED) and material decomposition capabilities. Certain other CT systems employ energy integrating (EI) detectors capable of operating at high X-ray flux rates. In certain implementations, however, the CT systems employ both PC and EI detectors such that the imaging system may combine energy information provided by ED detector cells with high flux capability and high signal-to-noise ratio (SNR) provided by the EI detector cells for use in reconstructing images.
Although the conventional detector cells provide varied functionality, a particularly challenging task is to configure detector settings for imaging a targeted ROI that is less than the full scan field of view (FOV) of the imaging system in high spatial resolution. By way of example, certain imaging modalities may need to generate high-resolution images of certain regions of the lungs, coronary vessels and/or tissues. As the lung field is adjacent to the coronary vessels and the sternum, high flux and low flux regions are proximally positioned and are encountered at the detector in rapid succession in time. Accordingly, application of conventional reconstruction methods may result in image blurring and other artifacts that can severely affect clinical diagnosis, especially if the imaged features are small. For example, plaques formed in coronary arteries are generally indicative of a risk of a potential heart attack, but are difficult to image due to their small size.
Certain conventional imaging systems, for example, have employed expensive detector configurations, heavier or higher power tubes combined with fast spinning of a gantry, and complex iterative reconstructions to generate high-resolution images. These techniques, however, incur considerable costs, are mechanically restrictive and/or rely on additional imaging time and radiation dosage, especially for reconstructing small features such as lesions and nodules in regions of interest.